Trump will be resoundingly defeated in court if he declares a national emergency (because there is none).

1) None of his claims of a crisis hold up to any scrutiny.

2) Congress is in session.

3) He hasn't finished using the money available for fencing.

4) The humanitarian issues at the border are Trump's own making.

The government will still need to be re-open!

He will be weaker than ever after being struck down, and Republicans will be on record for supporting giving the President tyrannical powers and abdicating their role in Congress.